This invention relates generally to the production of flexible, heat sealable, plastic bags and their subsequent filling and sealing, and in particular to a method and apparatus for forming a continuous web of sealed bags, the filling through a slit opening cut in each bag, and the heat sealing of the slits to reseal the bag for preserving an aseptic bag interior and for protecting the contents from contamination.
Flexible, heat sealable, bags formed with a lamination of Nylon or other strong flexible material, are extensively used in many industries and are particularly valuable for the packaging of fluids or fine granular materials. One important advantage of such packaging is that fluids such as juices, wines or the like are fully sealed against leakage in such a bag and, equally important, against the admission of air, gasses, moisture, or other objects that may damage the bag contents.
Flexible plastic bags for the storage and shipping of fluid products are generally formed with an attached fitment which opens into the bag for filling and eventual dispensing of the product. Often the filled bag is placed in a carton or other rigid container and a dispensing tap attached to an aperture in the carton is connected to the bag fitment for convenient dispensing of the contained product.
Flexible plastic bags or containers of the type described above have heretofore been manufactured by heat sealing the edges and by making lateral separations on two or more webs of thin heat sealable plastic. The sealed lateral bags are often separated by perforations for ease in separating the bags from the web and each bag in the web is provided with an attached open fitment for filling and dispensing, such as shown in U.S. Pat. No. 4,386,636.
If the plastic bags are to be used for comestibles or other products sensitive to contamination, bag sterilization is important. While container manufacturers can easily produce internally aseptic flexible plastic bags, those with attached unsealed fitments can readily become internally contaminated to possibly shorten the life or ruin the product to be contained therein. If internal bag contamination is an important consideration, the bag manufacturer can supply the bag webs with capped fitments. However, internally pre-sterilized bags with capped fitments must be sterlized externally around the cap and filling fitment in an aseptic chamber just prior to removal of the cap and the filling of the bag to ensure against contamination during filling in the filling chamber, and then replaced immediately after filling in an attempt to avoid damage or contamination of the product therein.
The flexible plastic bags made in accordance with the present invention are formed and then filled and sealed without use of such a filling fitment. By thus eliminating the filling fitment, exterior sterilization of a bag prior to filling is a simple and uncomplicated process in a sterilized chamber.
In the method and apparatus described herein, an internally presterilized plastic tube may be employed or, in a preferred embodiment, two identical webs of flexible, heat sealable plastic material may be sterilized before or after their joining in a conveyor where the combined webs are heat sealed along the edges to form a tube. The tube thus formed is then heat sealed across the bag separation positions, punched along the edges so that the web can be drawn through the conveyor system by rotating sprocket wheels, and laterally perforated along the heat sealed bag separations. If desired, the web of bags thus formed may be removed from the conveyor and folded in a storage container for future use; or if desired, the web may continue along the conveyer to receive an optional dispensing fitment, such as that disclosed in our copending U.S. patent application Ser. No. 447,493, filed Dec. 6, 1982. The fitment is heat sealed to the exterior surface of each bag, and its attachment is followed by the cutting of a lateral filling slit through only one sheet of the plastic, the admission of the product through a nozzle introduced through the slit, and the heat sealing of the lateral filling slit to thereby seal the bag from leakage of the product and the admission of air or external contaminants. It is important to note that internal sterilization is preserved both in bags fabricated from individual plastic webs and in bags fabricated from presterilized plastic tubes, and the subsequent addition of an optional dispensing fitment to their exterior surfaces cannot affect their aseptic interiors. Further, the bags do not become contaminated between the period of time from the lateral filling cut to the actual filling through the nozzle and the resealing of the filling cut immediately following the withdrawal of the nozzle if these operations are conducted in a sterile chamber.